Video shows moment wall collapses in Sydney blaze, sending fireball into sky

Firefighters have released stunning vision of the moment the wall of a Surry Hills building collapsed, unable to withstand the pressures of a ferocious fire that brought parts of Sydney to a standstill.

Like a slow-motion Hollywood stunt, birds flee as a metres-high chunk of wall at the top of the Randle Street complex, hollowed out by flames, begins to lean.

Within a second, the great hunk of concrete and steel is crumbling as it plummets seven storeys to the road below.

READ MORE: Massive building fire breaks out in central Sydney, sparks collapse

It smashes into parts of neighbouring buildings and finally hits the ground behind some temporary fencing, sending an enormous fireball shooting up the narrow alleyway and into the sky high above the building roofs.

The smoke glows orange as the power of the collapse dissipates into the air.

No one was nearby but 9News reporter James Wilson saw the whole thing.

"As we were running from one side of the street to the other, we heard this massive bang followed by this burst of flames and sparks and embers and that was a big chunk of this building collapsing.

READ MORE: Witness accounts from the ground

More confronting footage shared by Fire and Rescue NSW shows torrents of water being dumped on the blazing shell of a building, flames glowing clearly through the windows.

The still-burning carcass of an unluckily parked car melts below.

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